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Types of Tumors
Advances in Radiation Therapy
Symptoms
Advances in Surgery
FAQs
TYPES OF BRAIN TUMORS
Primary Brain Tumors
Those tumors that originate in the brain are called primary brain tumors. The most common type can start anywhere within the brain tissue. It originates from cells called glial cells that support and nourish the nerve cells, so such tumors are called gliomas. The most common type comes from glial cells called astrocytes, and such tumors are called astrocytomas. They can be very slow growing and take years to run their course, or they can be very aggressive and grow quickly, in which case they are called gliobalstomas. Even the more aggressive or malignant brain tumor do not ordinarily spread to other areas of the body, as do other malignant tumors. They cause damage by pressure on the brain or by infiltrating and destroying brain tissue.
One of the most common types of tumors that occurs within the head is a meningioma. This is not truly a brain tumor, since it grows from the coverings over the brain rather than the brain itself. Although this type of tumor is very benign and slow growing, it may reach a very large size before it is discovered. Often meningiomas can be removed surgically and may not recur. If the tumor is very large and causing a great deal of pressure on the brain, it may be necessary to remove the bulk of the tumor. If it involves important nerves or blood vessels, it may not be possible to remove all (or sometimes any) of the tumor without great risk of a neurological problem. In that case, the tumor or residual tumor may be treated with radiation. If it is small and does not involve any nerves, it may be treated with a single dose of stereotactic radiosurgery. If it is larger or pressing on nerves, Peacock stereotactic radiotherapy may be used. Meningiomas may be discovered even before they cause symptoms, since CT and MRI scans are being done so often for a variety of problems. If the meningioma is very small and not causing symptoms, it may be followed with periodic MRI, since sometimes meningiomas do not grow at all for many years.
Benign Tumors
There are other types of benign tumor that affect the brain. Several types originate in nerves just as they leave the brain. The most common is the type that develops on the vestibular branch of the acoustic nerve, which can cause loss of hearing in that ear. Although treatment has involved surgery in the past, more and more such tumors are treated with stereotactic radiosurgery, especially if they are discovered when they are small. Risk of additional loss of hearing or of damage to the facial nerve, that might cause paralysis of the muscles on one side of the face, is less with radiation than with conventional surgery.
Tumors can grow from the pituitary gland that lies in a hollow on the base of the skull just beneath the brain. Ordinarily pituitary tumors are benign, but they may cause hormone abnormalities. Pituitary or other tumors that grow in this area may press on the optic nerves and cause loss of vision or even blindness. Surgery can often be done by approaching these tumors through the nasal cavity to avoid injury to the overlying brain.
Metastatic Tumors
Very often a patient who has a malignant tumor anywhere in the body may have it spread or metastasize, in which case it is not uncommon for the tumor to spread to the brain. Sometimes there is only a single brain metastasis -- other times there may be many. The best treatment depends on how many tumors there are and their locations in the brain, the type of tumor, and whether there are malignant tumors elsewhere in the body. If there are one or two brain metastases, they might be removed surgically. Often stereotactic guidance can help localize the tumor to allow its removal through the smallest incision with the least risk to the surrounding brain. Sometimes stereotactic radiosurgery might be better for one or two (or even three) metastatic brain tumors, depending on their size and location, especially if deep within the brain, since it is less invasive than surgery. Depending on the type of tumor and the number of brain metastases, a course of radiation to the entire brain may be used also, in order to treat even microscopic tumors that cannot be identified with MRI. Chemotherapy is usually used with such metastatic disease to treat both the brain metastases and tumors that may have seeded elsewhere in the body.
ADVANCES IN RADIATION THERAPY FOR BRAIN TUMORS
There have been recent advances in techniques to treat brain tumors with radiation. The limiting factor in radiating brain tumors is the limit of how much radiation the near-by normal brain tissue can tolerate. Within the past few years, a stereotactic conformal radiotherapy program, called the Peacock system, has been used for many St. Luke's Episcopal Hospital patients and is available at only a few hospitals. This system allows the radiation oncologist to plan on a computer how much radiation each part of the brain will receive. That makes it possible to provide the maximum, dose to the maximum dose to the brain tumor while still protecting other sensitive parts of the brain from excess radiation.
Another recently developed radiation technique has been introduced: X-Knife Stereotactic Radiosurgery. This system provides a single large dose of sharply localized and accurately targeted radiation, equivalent to the Gamma Knife. It can be used to treat small areas of tumor that might remain after surgery or show as the first sign of recurrence a brain tumor. In addition, it can be used to treat metastatic brain tumors or even certain types of benign tumors occurring within the skull.
SYMPTOMS
The symptoms that occur with brain tumors depend on where they are located within the brain. If they begin in the motor area, they can cause weakness of an arm or leg very early in their course. They may occur in the part of the brain concerned with speech and cause problems with speech or loss of speech. On the other hand, they may originate in silent areas and not cause any symptoms until they are quite large and far advanced. A brain tumor in almost any location can cause convulsions or seizures, which may be anything from momentary lapses of awareness or function to unconsciousness with shaking movements. When a tumor becomes large, the presence of a mass of tumor tissue within the head may cause the pressure to increase, which may cause confusion, drowsiness, visual difficulty or even coma.
Treatment for gliomas most often involves surgery to remove as much of the tumor as possible. Unfortunately, even if it appears that a gliomas has been completely removed, it almost always recurs, because there are microscopic islands of tumor cells scattered throughout the entire region of the brain.
ADVANCES IN SURGERY FOR BRAIN TUMORS
There have been recent advances in surgery for brain tumors. Stereotactic or computer guidance may allow the surgeon to approach the tumor from the safest approach possible and remove more tumor tissue with less injury to surrounding brain tissue than with conventional techniques. Some brain tumors look just like normal brain tissue, but MRI or CT scanning can help define the limits of the tumor and stereotactic techniques allow the surgeon to use that information directly in the operating room to help guide the surgery. St. Luke's Episcopal Hospital has an advanced 3-dimensional stereotactic surgical guidance system, developed by Dr. Gildenberg, which provides an amount of information available at only a few centers in the U.S.
Advances in Chemotherapy for Brain Tumors
There has been a recent advance in treatment of malignant gliomas in that a chemotherapy agent might be instilled in the operating room directly into the cavity that remains when tumor tissue has been removed. Although this technique has only recently been introduced, early testing suggests that it significantly increases the time before the tumor might recur and prolongs survival.
Some types of glioblastomas respond to certain chemotherapy programs. A new chemotherapy agent for glioblastomas has just been approved during this past year. The best chemotherapy must be designed for each patient, depending on the type of tumor, the severity of neurological problems the patient may have, and the patient's general medical condition.
Multidisciplinary Care
Since treatment of brain tumors requires a great deal of coordination between surgical and radiotherapy techniques, Dr. Gildenberg works closely with Dr. Shiao Woo, radiation oncologist. They see patients together and follow patients with periodic MRI scans, so the tumor might be treated at the first sign of recurrence. Each program is designed for the individual patient's needs, and may involve additional surgery, sometimes with associated local chemotherapy, or with stereotactic radiosurgery.
FREQUENTLY ASKED QUESTIONS
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What symptoms does a brain tumor cause?
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That depends on the part of the brain the tumor occurs and whether it is causing an increase in the pressure within the head. If the tumor occurs in an area that controls movement of the hand or arm, it can cause weakness or paralysis of that extremity. If it involves the area associated with speech or memory, it can cause loss of those functions. If it occurs in a silent area, it may not produce any symptoms until it is far advanced. If it causes an increase in pressure within the head, it may cause headache, confusion, poor memory, drowsiness, and eventually unconsciousness.
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How can you tell a headache from a brain tumor?
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Most headaches are not caused by brain tumors. If a person has had headaches for a long time, especially if associated with stress or allergies, it is unlikely to be from a tumor. If a headache occurs in someone who does not ordinarily have headaches or is accompanied by any neurological symptoms, even forgetfulness or poor mental function, a brain tumor might be considered.
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Is a brain tumor always fatal?
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Some types of brain tumors, such as glioblastomas, are so persistent and aggressive that they always recur and are eventually fatal. Other tumors, such as meningiomas, are benign and can often be cured by surgery or radiation. Metastatic brain tumors can often be controlled, but the patient may already have widespread disease which is eventually fatal cancer.
Last Updated: January 26, 2001
Source: Philip L. Gildenberg, M.D., Ph.D.
Texas Cancer Institute®
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